[Greenbuilding] A "green", walkable, low-slope roof membrane?

[Speireag Alden]

Sgrìobh George J. Nesbitt:

>In the age of global warming, it is even cooler to be a cool roof.
>(green isn't as reflective)

     I'm skeptical.  A living roof has mass and thickness which will 
retard the conduction of any solar gain into the living space.  Also, 
the living plants transpire moisture, which cools the roof.  The 
grass will absorb the solar energy and then radiate it in all 
directions, being three-dimensional.  Finally, the grass converts 
some small percentage of sunlight to chemical energy, which means 
that it's not available to heat up the roof.

     I've been under the plywood of my roof when there's earth on top 
and when there's not.  No earth on a sunny day means palpable 
radiated heat on the underside of the decking.  Earth on a sunny day 
means no perceptible incoming heat.

-Speireag.

-- 
The chill's in the air
Even so, we are gaining
on Old Man Winter.

-Speireag.